It is a very cool looking bike. Not sure about the tricycle handlebars?
Many years ago I made a similar bike for my son. When I say many years ago, it was "many, many years ago", he's 56 now, LOL. What I found out from my exercise is that kids are not only small and short "little people", they also have not developed the coordination to operate a coaster brake when they fit a 12" bike. A small 12" bicycle or a 10" tricycle is much safer with a fixed gear hub. As they grow into a 16" wheel sized bike they also develop their coordination skills to operate a coaster brake. We lived on a hilly street and the driveway had a grade. I gave him the bike and off he went pedaling, but he could not grasp the skill of back pedaling to operate the brakes. It was a close call.
John